A Frequency Identification–Based Adaptive Controller Design for Active Damping of a Photovoltaic Grid‐Tied System With Nonlinear Loads

ABSTRACT The interaction between the photovoltaic (PV) grid‐tied inverter, nonlinear loads, and the grid in a PV grid‐tied system with nonlinear loads may result in oscillations. Changes in the power of nonlinear loads and the grid equivalent impedance can cause an uncertain shift in the oscillation frequency. To address this problem, this research proposes an adaptive active damping (AAD) control strategy that can adjust to changes in oscillation frequency. First, the sequence impedance model of a PV grid‐tied system with nonlinear loads is established using the harmonic linearization method, and the resonance properties of the system are analyzed using the Nyquist stability criterion. Subsequently, based on negative‐resistance theory, impedance relative sensitivity is derived to identify the key factors influencing the resonant properties, serving as a guide for the design of the damping controller. Moreover, an AAD controller is designed based on oscillation frequency identification using a combination of variational mode decomposition (VMD) and Hilbert transform (HT). Compared with the traditional proportional capacitor‐current‐feedback active damping (PCCF‐ AD ) control, the proposed adaptive method effectively overcomes the poor damping effect caused by oscillation frequency offset. The effectiveness of the strategy is verified through simulation analysis.